Abstract 10787: Discovery of a Novel Aptamer-based Inhibitor of GPVI and its Matched Active Control Agent
Introduction: GPVI mediates collagen induced platelet activation and is required for firm adhesion of platelets to the damaged vessel wall. GPVI is also overexpressed in type 2 diabetes, and high GPVI levels are associated with onset of ACS and TIAs, making GPVI an attractive target for new antiplatelet agents. Active control of the intensity and duration of antiplatelet therapy is anticipated to provide significant clinical benefit. Therefore we sought to identify actively controllable inhibitors of GPVI using aptamer-control agent technology.
Methods: Aptamers to GPVI were isolated via the SELEX process, ranked by affinity, and screened for anti-GPVI activity in collagen induced platelet aggregation assays. Aptamer hits were optimized for potency and stability in the body. Aptamer control agents were designed based upon Watson-Crick basepairing rules and tested for aptamer neutralization in platelet aggregation assays. Aptamers were further evaluated for inhibition of platelet adhesion to collagen coated surfaces under high shear in human whole blood.
Results: GPVI aptamers inhibited collagen and CRP mediated platelet aggregation. Optimization yielded a potent, fully stabilized aptamer composition (RB571; Kd of 5 nM). RB571 inhibited CRP induced aggregation of platelets with an IC50 of 30 nM (see Figure) and potently inhibited platelet adhesion to collagen coated surfaces under high shear. A rationally designed active control agent to RB571 (RB515) dose dependently reversed RB571 inhibition of platelet aggregation within 10 minutes (See Figure).
Conclusions: We identified a potent aptamer-based GPVI antagonist and an active control agent which can be used to rapidly control its pharmacologic activity. This represents the first identification of an actively-controllable GPVI antagonist. Preclinical and clinical studies will be performed to evaluate this controllable approach to a unique target to offer acute and subacute antiplatelet therapies.
- © 2010 by American Heart Association, Inc.